Today's intelligent optical networks allow carriers to offer not only the traditional permanently provisioned bandwidth services but also the dynamically provisioned bandwidth-on-demand (BoD) services and optical virtual private network (O-VPN) services resulting in a more cost-effective service layer network. Deploying a BoD service requires the implementation of control plane signaling and routing protocols. Standards for interoperable control plane implementations are being developed by the OIF, the IETF, and the ITU. The OIF generated a specification for an optical user-to-network interface (O-UNI) (See, for example, OIF Implementation Agreement “UNI 1.0 Signaling Specification”, The Optical Internetworking Forum, October 2001). The effort in IETF, which is under the generalized multi-protocol label switching (GMPLS) umbrella, resulted in the generation of an architecture document (IETF Draft “Generalized Multi-Protocol Label Switching (GM-PLS) Architecture”, work-in-progress draft-ietf-ccamp-gmpls-architecture-03.txt, August 2002.) and is finalizing a number of routing, signaling, and link management specifications. The ITU is also undertaking a similar effort under the automatically switched optical network (ASON) umbrella (ITU-T Recommendation G.8080 “Architecture for the automatically switched optical networks (ASON)”, International Telecommunications Union, November 2001). These efforts at the standards bodies are progressing, and the goal of interoperability will be assessed when these protocols are deployed in the field.
Given that data traffic (in particular IP traffic) is becoming predominant, IP router connectivity is increasingly provided by wavelength services at OC-48/OC-192 rate and soon OC-768 (40 Gbps). Consequently, IP routers are expected to be the primary client devices attached to the optical network. It is worth noting however, that typically the BoD requests are due to finer granularity dynamic connection activity at the IP flow level such as MPLS traffic engineered flows or label switched paths (LSPs) which typically originate at a non-core router. The core routers multiplex a number of these IP flows over a wavelength connection through the optical network. In addition, dynamic wavelength services will be needed to support BoD for future high bandwidth applications (optical dial-tone). In the conventional IP-over-optical reference model, the optical network consists of OXCs (which are discrete or stand-alone switching elements, typically with an O-E-O switching fabric) connected by WDM point-to-point links. In this model, every wavelength is converted to the electronic domain at each node (i.e., there is no optical bypass) even if the majority of the wavelengths entering each node are not carrying traffic that is destined for that node (this is known as the transit traffic). With the advent of ultra long reach optical transmission and optical bypass capabilities, optical signals can travel long distances, and optically bypass several intermediate nodes without converted to the electronic domain at intermediate nodes. Accordingly, for transit traffic, it is not necessary to electronically terminate every wavelength entering a node (for instance the A-C connection shown in FIG. 3 optically bypasses site B). Since O-E-O conversion is not needed for the wavelengths that optically bypass a node, fewer transmitter and receiver (TxRx) interfaces are needed and a smaller OXC size is required, which results in a dramatic reduction in the overall network cost (See, for example, A. A. M. Saleh, “Transparent Optical Networking in Backbone Networks”, in Proceedings of OFC 2000, paper ThD7, March 2000.).
A framework that captures such paradigm is that of a two-layer optical network architecture; a reconfigurable OXC layer (where the OXC, is a wavelength-granularity switch which could be based on an electronic (O-E-O) or optical (O-O-O) switching fabric) that provides the cross-connection functionality, over a reconfigurable all-optical layer (where reconfigurability is accomplished through integrated all-optical switches and optical add/drop multiplexers as well as tunable line TxRx interfaces) that provides efficient transport capability. This architecture is depicted in FIG. 3.
Since the optical reach in a given network is dependent on a number of parameters (fiber characteristics, chromatic dispersion, nonlinear effects, etc.), there is always a limit on how far an all-optical connection can extend. When this limit is reached, the optical signal has to be regenerated before being able to propagate further. Accordingly, if the distance between the end-nodes is more than the system reach in the optical domain, two or more optical segments must be concatenated to form an end-to-end connection. This concatenation or cross-connection can be accomplished dynamically and automatically by the OXC (the A-D connection in FIG. 3 requires a cross-connection at site C to cross-connect the A-C and C-D segments). In the absence of such OXC, this cross-connection is accomplished manually by connect a receiver to a transmitter either directly or via a fiber patch panel, or by using a regenerator that include both the receiver and transmitter along with signal regeneration processors.
The present invention addresses optimal port allocation strategies to dimension the OXCs in support of BoD wavelength services with a given target performance expressed in terms of average connection blocking probability in an optical network based on the aforementioned two-layer architecture. Those and other embodiments of the present invention will be described in the following detailed description. The present invention addresses the needs described above in the description of the background of the invention by providing improved systems, devices, and methods. These and other teachings, variations, and advantages of the present invention will become apparent from the following detailed description of the invention.